Hydraulic system for controlling the return movement of pressure pads in air cushionpresses



Dec. 22, 1959 F. M. WILLIAMSON 2,918,272

HYDRAULIC SYSTEM FOR CONTROLLING THE RETURN MOVEMENT OF PRESSURE PADS INAIR CUSHION PRESSES Filed Feb. 16, 1959 JNVENTOR.

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f/ay/ 1447/242745102 United States Patent O HYDRAULIC SYSTEM FORCONTROLLING THE RETURN MOVEMENT OF PRESSURE PADS IN AIR CUSHION PRESSESFloyd M. Williamson, Detroit, Mich.

Application February 16, 1959, Serial No. 793,500

6 Claims. (Cl. 267-1) This invention relates to hydraulic'systems fordelaying the return movement of pressure pads in a ram press employingan air cushion. t

In such presses it is frequently desirable to delay the return movementof the pressure pad or to stop the pad at some intermediate position inits upward travel to prevent distortion of the workpiece being formed.The invention herein disclosed provides a simple and effective means forcarrying out this type of operation.

A principal object of the invention therefore is to provide a hydraulicsystem fordelaying return movement of a pressure pad in a ram presshaving an air cushion.

Other and further objects of the invention will be apparent from thefollowing description and claims and may be understood by reference tothe accompanying drawing which by way of illustration shows a preferredembodiment of the invention and what I now consider to be the best modeof applying the principles thereof. Other embodiments of the inventionmay be used without departing from the scope of the present invention asset forth in the appended claims. The single figure of the drawingschematically illustrates a ram press with a hydraulic system embodyingthe invention.

Such a press includes a reciprocable ram 10, a fixed bolster 12, and anair cushion 14 comprising an air cylinder l6 and a piston 18 arranged toreact upon a pin plate 20 disposed beneath the bolster 12. A lower diewhich is mounted on the bolster 12 includes a fixed section 22surrounded by a pressure pad 24 between which and the pin plate 20 aseries of pins 26 are disposed whereby the pad 24 is supported by thepin plate 20, which in turn is supported by the piston 18 of the aircushion. A die 28 mounted on the ram 10 to move therewith is cooperablewith the die sections 22 and 24 for shaping a flat sheet metal blank 30.When the press is open the pad 24 is positioned so that its uppersurface is at the same elevation as the upper flat surface of thesection 22. A suitable adjustable pressure regulating valve 32 isdisposed in the air pressure line 34 through which air under say, forexample, I pounds per square inch, provided by air under pressuresupplied through the air line 40 under the control of a suitableadjustable pressure regulating valve 42.

One or more hydraulic cylinders 44 are mounted on I the bolster 12around the pressure pad 24, and each includes a cylinder 46 and a piston48 having its rod 50 slidahly extending through a bore in the bolster 12and arranged to react on the pin plate 20. Each cylinder 46 is connectedby a fluid pressure line indicated generally ice at 52 with the tank 36,such line including pipe 54, passages 56, 58, cylindrical bore 60, andpassage 62 in the automatic valve unit 64, and conduit 66 communicatingat one end with the passage 62 and at its other end with the interior ofthe tank 36 at the bottom thereof whereby hydraulic fluid, i.e. oil,under the pressure to which it is subjected in the tank will be suppliedto each of the cylinders 46. The total pressure of the cylinders 46under only the pressure to which the oil in thetank 36 is subjected isless than the pressure exerted by the air cushion 14 against thepressure pad 24.

An air pressure operated hydraulic booster 68 is arranged and operablewhen energized to increase the total pressure developed by the highpressure cylinders 44 to a value in excess of the pressure exerted bythe air cushion 14 on the pad 24 whereby the pressure developed by thecylinders 44 is effective to delay the return of the air cushion 14 uponthe opening of the press and hence the return of the die pad 24 to itsupper position. At times it is necessary to delay the return of the pad24 or to stop the pad 24 at some position in its upward travel so as toprevent distortion of the workpiece being formed. Thus so delaying thepressure pad will cause the workpiece to cling to the die section 22upon opening movement of the press.

The booster 68 includes an air cylinder 70 having a piston 72reciprocable therein, the cylinder 70 being connected by air pressureline 74 to the line 40 through which air pressure is supplied to thetank 36. A rotary valve'78 controls the supply of air under pressurethrough the line 74 to the cylinder 70 and the porting of the cylinder70 to atmosphere. The booster includes a hydraulic booster cylinderhaving a piston 82 reciprocable therein, the piston 82 being connectedby stem 84 to the piston 72 so as to move therewith. The piston 72 hasan effective area substantially greater (say, for example, ten times)than the piston 82. The cylinder 80 is connected by a hydraulic fluidline indicated generally at 86 with the oil under pressure in the tank36, such line including the conduit 66 and in the valve 64 the passages62, 88, 90, 92 and 94, the latter of which communicates with the end ofthe cylinder 80. A check valve 96 in the line 86 permits flow ofhydraulic fluid from the tank 36 under the pressure therein into thecylinder 80 but prevents return flow.

The passage 94 communicates with one end of the bore 60. A valve 98slidable in the bore 60 is biased by a spring 100 to a position to closethe end of the passage 94 opposite the cylinder 80. The bore 60communicates through a port 102 with a passage 104 which communicateswith the passage 56. Thus when the valve member 98 in response to thedischarge of fluid from the cylinder 80 moves against the force of thespring 100 sufficiently to uncover the port 102, fluid will flow fromthe cylinder 80 through the passage 94, the bore 60, the port 102, thepassage 104, the passage 56, and the conduit 54 toward the cylinders 46thereby to transmit the pressure of the fluid in the cylinder 80 to thehydraulic fluid in the cylinders 46.

When the booster 68 is not energized, the air piston 72 will normally beat or adjacent the bottom of the cylinder 70. However, when the valve 78is positioned so as to supply air under pressure through the line 74 tothe cylinder 70, the piston 72 will be effective to advance the piston82 in the cylinder 80 whereby the fiuid discharged from the cylinder 80moves the valve member 98 upwardly sufficient to cause the same to closethe end of the passage 62, thereby shutting off the communicationbetween the tank 36 and the cylinders 46, and then upon further upwardmovement of the valve member 98 to uncover the port 102 for the purposeof transmitting the pressure thus developed by the piston 82 to thecylinders 546. 'As previously noted, the pressure developed in thecylinders 46 is in excess of the upward thrust of the air cushion 14.

The valve 78 includes a rotary body 110 having passages 112 and 114therein, the body 110 having fixed to it an arm 116 havinga pin'and slotconnection 118 with a link 120 which is fixed to the ram for movementtherewith. Upon the closing'of the press-the mechanical linkage betweenthe ram 10' and the valve body 110 will rotate the latter so that thepassage 112 will establish communication between the air pressure lines40 ;and 74, thus admitting air under pressure to the cylinder 70 toadvance the piston 72 thereof. 6 Since the cylinders -46 and 80 werepreviously in'comrnunicationwith the tank 36, the cylinders 46 andSO-will be charged with hydraulic fluid under the pressure to which theyare sub- I jected by the air pressure in the tank 36. Thus when thepress closes, that is, with the parts of the press ar- 1 ranged as shownin the drawing, the air pressure operated hydraulic booster 68 will'beenergized so as to shift the valve member 98 to shut off thecommunication between the cylinders 46 and the tank 36 and then to openthe communication between'the cylinder 80 and the cylinders 46, thusincreasing the pressure in the cylinders 46 to a value. sufficient tocounteract the air cushion 14, thus delaying return movement of the pad24.

'As the ram moves upwardly, that is, as it retracts,

the pin and slot connection 118 will shift the valve body 110 through 90in a clockwise direction so that the passages 112 and 114 will port theair pressure line 74 to atmosphere through the atmospheric vent 122,thusdissipa'ting the pressure in the cylinder 70. The pressure exertedon the pistons 48 by the air cushion 14, through the piston 18, the pinplate 20 and the piston rods 50, will ddisplace hydraulic fluid from thecylinders 46 through the conduit 54, the passage 56, the passage 104,the port'102, the bore 60, and the passage 94 to the cylinder 80. Sinceboth sides of the valve member 98 will be exposed to the same pressure,the spring 100 will be free to shift the valve member 98 so as to closethe port 102 and to expose the end of the passage 62, thereby permittingthe return of fluid from the cylinders 46 through the fluid ipressureline 52 to the tank 36. As soon as the pressure 7 'in'the air cylinder70 is dissipated, hydraulic fluid will flow from the tank 36 through theline 86 into the cylinder 80. Since return of the valve member 98 to itslowermost position will leave the cylinders 46 in communication with theoil in the tank 36, the cylinders 46 will always be charged withhydraulic fiuid under the pressure of the hydraulic fluid in the tank36. The'circulation of oil obtained by reason of the operation of thebooster 68 will serve to dissipate heat from the oil.

Thus the system provides an effective means for delaying the returnmovement of the pad 24 under the influence of the air cushion 14. It iscontemplated that the mechanical connection between theram 10 and thevalve body 110 may be temporarily bro-ken so as to permit .manualcontrol of the valve 110 whereby the return of the "pad 24 can bemanually controlled for checking purposes.

While I have illustrated and described a preferred embodiment of myinvention, it is understood that this is capable of modification and Itherefore do not wish to be limited to the precise details'set forth butdesire to avail myself of such changes and alterations as fallwithin thepurview of the following claims.

I "claim: v g 1. in a ram press having a fixed bolster, a movablehydraulic fluid under pressure therein, a hydraulic booster cylinder, afluid pressure line between said tank and "cylinder through whichhydraulic fluid from the tank is supplied to said cylind'er,acheck'valve in said line to prevent return flow of fluid therethrough,an air cylinder having a piston therein, a piston in said hydrauliccylinder connected to said air piston so as to move therewith, a highpressure hydraulic cylinder and piston associated with the bolster ofthe press and arranged so as to counteract said air cushion, a hydraulicline between said tank and said high pressure hydraulic cylinder, ahydraulic fluid line between said booster hydraulic cylinder and saidhigh pressure hydraulic cylinder, valve means in said last-mentionedline permitting fluid fiow therein from said booster hydraulic cylinderto said high pressure hydraulic cylinder, said valve means including avalve actuated by the discharge of hydraulic fluid rorn said boosterhydraulic cylinder to close the hydraulic fluid line between said tankand said high pressure hydraulic cylinder whereby such discharge ofhydraulic fluid increases the pressure of the hydraulic fluid in thehigh pressure'hydraulic cylinderto a value sufiicient to counteract saidair cushion, an air pressure lineconnected to said air cylinder having avalve therein operated upon closing of the press to open such line tothe flowof air under pressure to the booster air cylinder for causingthe piston thereof to actuate the piston of saidhydraulic boostercylinder to discharge hydraulic fluid therefrom, said last-mentionedvalve in another position thereof being adapted to port the line leadingto said booster air cylinder to atmosphere upon the opening movement ofthe press.

2. In a ram press having a fixed bolster, a movable pressure padarranged to be moved toward the bolster by the press ram upon theclosing of the press and an -air cushion reacting on said pad to resistsuch movemerit and to move such pad away from the bolster upon openingof the press: a hydraulic system for controlling the return movement ofsuch pad comprising a tank hav- I ing hydraulic fluid therein, ahydraulic booster cylinder, a

fluid pressure line between said tank and cylinder through whichhydraulic fluid from the tank is supplied to said cylinder, a checkvalve in said line to prevent return flow of tuid therethrough, an aircylinder having a piston therein, a piston in said hydraulic cylindersmaller than said air piston and connected thereto so asto movetherewith, a source of air pressure connected to said tank above thehydraulic fiuid therein, a high pressure hydraulic cylinder and pistonassociated with the bolster of the press and arranged when actuated soas to counteract said air cushion, a hydraulic line between said tankand said high pressure hydraulic cylinder through which hydraulic fluidis supplied to such' cylinder from said tank, a hydraulic fluid linebetween said booster hydraulic cylinder'and said high pressure hydrauliccylinder, valve means in said last-mentioned line permitting fluid flowtherein to said high pressure hydraulic cylinder, said valve meansincluding a valve adapted by the discharge of hydraulic-fluid'from saidbooster hydraulic cylinder in response to actuation of the air piston inthe booster cylinder to close the hydraulic fluid line between said tankand said high pressure hydraulic cylinder whereby such discharge ofhydraulic fluid increases the pressure of the hydraulic fiuid in thehigh pressure hydraulic cylinder to a value suflicient to counteractsaid air'cushion, an air pressure line between sald source and said aircylinder having a valve therein adapted in one position thereof to opensuch line to the flow of air under pressure to the booster air cylinderand a connection between said last-mentioned valve and a part of thepress movable with the ram for operating said valve, said lastmentioned'valve in another position thereof being adapted to port the lineleading to said booster air cylinder to atmosphere upon the'openingmovement of the press.

3. in a ram press having a fixed bolster, a movable pressure padarranged'to be movedtoward the bolster by the press ram upon the closingof'the press and an air cushion reacting on'said pad toresist suchmovement and to move such pad away from the bolster upon opening of thepress: a hydraulic system for controlling the return movement of suchpad comprising a tank separate from the air cushion and having hydraulicfluid under pressure therein, a series of high pressure hydrauliccylinders and pistons mounted on the top side of the bolster of thepress and disposed around the pressure pad and arranged to react whenenergized on said air cushion for counteracting the same, a hydraulicline between said tank and said high pressure hydraulic cylindersthrough which hydraulic fluid is supplied to said cylinders from saidtank, a normally open valve in said line, an air pressure operatedbooster connected with said line between said valve and said highpressure hydraulic cylinders and operable when energized to react on thehydraulic fluid therein for closing said valve and increasing thepressure of the hydraulic fluid in the high pressure hydraulic cylindersto a value suflicient to counteract said air cushion, an air pressureline connected to said booster for energizing the same and a controlvalve therefor adapted upon closing of the press to open such line tothe flow of air under pressure to the booster and to port said line toatmosphere upon opening of the press.

4. In a ram press having a fixed bolster, a movable pressure padarranged to be moved toward the bolster 'by the press ram upon theclosing of the press and an air cushion reacting on said pad to resistsuch movement and to move such pad away from the bolster upon opening ofthe press: a hydraulic system for controlling the return movement ofsuch pad comprising a tank having hydraulic fluid therein, an airpressure operated hydraulic booster including a cylinder, a fluidpressure line between said tank and cylinder through which hydraulicfluid from the tank is supplied to said cylinder, means to preventreturn flow through said line, a source of air pressure connected tosaid tank above the hydraulic fluid therein, a high pressure hydrauliccylinder and piston associated with the bolster of the press andoperable so as to counteract said air cushion, a hydraulic line betweensaid tank and said high pressure hydraulic cylinder, a hydraulic fluidline between said booster hydraulic cylinder and said high pressurehydraulic cylinder, valve means in said last-mentioned line permittingfluid flow therein from said booster hydraulic cylinder to said highpressure hydraulic cylinder, said valve means including a valve actuatedby the discharge of the hydraulic fluid from said booster hydrauliccylinder to close the hydraulic fluid line between said tank and saidhigh pressure hydraulic cylinder whereby such discharge of hydraulicfluid increases the pressure of the hydraulic fluid in the high pressurehydraulic cylinder to a value suflicient to counteract said air cushion,and a valve associated with said booster and controlled by opening andclosing movement of the press for controlling the operation of saidbooster.

5. Apparatus according to claim 4 wherein said valve actuated by thedischarge of hydraulic fluid from said booster hydraulic cylinder formsa check valve to prevent return flow of hydraulic fluid in saidlast-mentioned line from said high pressure hydraulic cylinder to saidbooster hydraulic cylinder.

6. Apparatus according to claim 4 wherein said means to prevent returnflow through said fluid pressure line between said tank and boostercylinder includes a check valve in said fluid pressure line.

References Cited in the file of this patent UNITED STATES PATENTS RodeDec. 1, 1931 McMillin et a1 July 14, 1942

